The present disclosure generally relates to implementation of a Fresnel hot mirror, and specifically relates to implementation of an immersed Fresnel structure with a curable liquid polymer.
A Fresnel hot mirror can be used in virtual reality systems as part of the eye tracking process, i.e., the process of detecting direction of a user's gaze, which may comprise detecting an orientation of an eye in 3-dimensional (3D) space. The Fresnel hot mirror can be used to redirect light reflected from the eye to a camera used to image a reflection of light from at least one surface of the eye. The Fresnel hot mirror can be implemented as an immersed Fresnel mirror. In one approach, the immersed Fresnel mirror can be implemented by using an index matching fluid packaged into a molded Fresnel structure. However, this approach is impractical from the manufacturing ability perspective and liability perspective (e.g., product shipping is extremely difficult). In another approach, the immersed Fresnel mirror can be implemented by molding an index-matched fluid and a Fresnel structure separately and then using an index matching glue to attach the fluid to the Fresnel structure. However, this approach is also impractical from the manufacturing perspective. For example, it is very difficult to manufacture the fluid structure and the Fresnel structure having matching shapes. In addition, a certain level of unevenness is present on Fresnel tips, as well as inclusions in the fluid structure.